IAC 1-7-08
Accelerator: 100 ns, 60 Hz, 15 MeV
Configuration: Collimated rear scint + 2" Aluminum brick
Rates:
- Coinc both PMTs =484/4min = 121/min
- PMT Coinc Both PMTs & Metallica DC =25/4min = 6/min
Configuration: Collimated rear scint
Rates:
- PMT Coinc both PMTs = 308/2min = 154/min
- PMT Coinc Both PMTs & Metallica DC =17/2min = 8/min
The ratio of double/triple =36/1054 = 3.1%
Configuration: Collimated rear scint+ 2" Aluminum brick + 2" lead brick
Rates:
- PMT Coinc both PMTs=105/10min = 10/min
- PMT Coinc Both PMTs & Metallica DC =4/10min = 0.5/min
We see a lot of events in the Scintillator and very few in the Chamber. There is no clear electron signal so let's debug the beamline.
Our tests on Friday showed that inserting an Aluminum brick in front of our first collimator decreased the first scintillator's count rate by approximately 60 %. A 15 MeV electron should stop in 2cm of Aluminum. We believe our 2" (5 cm) thick Aluminum brick will stop electrons but not photons. We do not observed the same change in rate when we insert the Aluminum brick in front of the rear scintillator. We believe our collimation system is blocking most of the electrons.
We insert an Aluminum brick in front of the first scintillator.
Aluminum block in front of first scintillator between experimental side wall and large scintillator is in place we did not remove the Aluminum block in front of the 2nd (last) scintilaltor.
Rates:
- First PMT singles =6128/2 min = 3064/min
- PMT Coinc both PMTs=132/2 min = 66/min
- PMT Coinc Both PMTs & Metallica DC =3/2min = 1.5/min
Now take the brick out.
Rates:
- First PMT singles = 6949/2min = 3474/min
- PMT Coinc both PMTs= 183/2min = 91/min
- PMT Coinc Both PMTs & Metallica DC =3/2min = 1.5/min
Electrons are a small fraction of our signal.
We remove the 1/6" collimator in front of the first scintillator paddle. Rates:
- First PMT singles = 3795/min
- PMT Coinc both PMTs= 145/min
- PMT Coinc Both PMTs & Metallica DC =46/min
We move the drift chamber 3.6 cm beam left (toward counting house wall) and removed Aluminum brick in front of the last scintillator. Now there is only a 1/4" diameter collimator on the Accelerator side of the wall and a 1/8" diameter collimator in front of the last scintillator.
Rates:
- First PMT singles = 3771/min
- PMT Coinc both PMTs= 220/min
- PMT Coinc Both PMTs & Metallica DC =67/min
Now we return:
Give Kevin the front PMT, he changes the dipole to maximize output, then he lowered the current to minimize pile up. This dipole setting corresponds to 20 MeV electron energy.
Aluminum block out:
Rates:
- First PMT singles = 7582/2 min =3791/min
- PMT Coinc both PMTs= 25/min
- PMT Coinc Both PMTs & Metallica DC =1/min
Aluminum block in:
- First PMT singles = /min
- PMT Coinc both PMTs= /min
- PMT Coinc Both PMTs & Metallica DC =/min